Systems and methods for preventing contamination of recorded biological signals during surgery

ABSTRACT

A system for recording, processing, and monitoring biosignals is provided, the system being configured to suspend data acquisition whenever an electric surgical tool or other generator of high frequency interference is in use. Such a system may protect the hardware of the system and reduce or eliminate the acquisition of distorted signals. The system of some embodiments includes an amplifier system configured to detect the presence of high frequency interference. Related methods are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a National Stage of International ApplicationNo. PCT/US2014/058494, filed Sep. 30, 2014, which claims the benefit ofU.S. Provisional Patent Application No. 61/884,525 entitled “MEANS OFPREVENTING CONTAMINATION OF SSEP SIGNALS DURING SURGERY” filed on Sep.30, 2013, the disclosures of which are expressly incorporated byreference herein in their entirety.

FIELD

The present technology relates generally to the field ofelectrophysiology. In particular, the technology relates to devices,systems, and methods for filtering out noise during the recording and/orprocessing of biosignals.

BACKGROUND

Eliciting and tracking evoked potentials during surgery is anestablished method for monitoring for potential nerve injuries. Forexample, electrically stimulating a patient during surgery andmonitoring the resultant somatosensory evoked potentials (SSEPs) usingconventional intraoperative neurophysiologic monitoring (IONM) systemsis an accepted and useful clinical procedure that can identify changesin brain, spinal cord, and peripheral nerve function. Conventional IONMsystems are typically used when the risk of severe nerve damage isrelatively high, such as, for example, during brain and spinalsurgeries. Early and accurate identification of changes in nervoussystem functioning may minimize the occurrence of long-term damage tostructures of the nervous system.

Similarly, improved neurophysiologic monitoring devices and methods havebeen developed, which can be used to stimulate and monitor a patient'sevoked potentials during other surgeries in order to identify andprevent positioning effect injuries. Such devices and methods aredescribed in U.S. Pat. No. 8,731,654 to Johnson et al., the disclosureof which is herein incorporated by reference in its entirety.Positioning effect injury is an injury caused by undue tension orpressure on peripheral nervous structures. It can be caused by theposition in which a patient is placed during surgery. Warning signs ofpositioning effect may include sensations, such as, for example,numbness, tingling, or weakness in a portion of the body. Duringsurgery, a patient is typically placed under general anesthesia andunable to identify or react to the usual warning signs of positioningeffect. Consequentially, patients may be left in compromised positionsfor the duration of a surgical procedure. Continued trauma frompositioning effect may result in prolonged or even permanent injury toone or more peripheral nerves.

Intraoperative neurophysiologic monitoring is generally performed with aspecialized computing device that delivers electrical stimulations to apatient's body and records signals produced by the body in response.Alternatively, spontaneously arising signals that do not requirestimulation may be recorded. The specialized computing device typicallyperforms some processing of the recorded signal(s), and healthcareprofessionals may monitor the processed signal for changes.

In order for monitoring to be effective noise and interference should beminimized. Reducing noise and interference is a particular concern whenthe target signals are very small such as with evoked potentials,because even the presence of a little noise can dramatically reduce thesignal-to-noise ratio due to the small size of evoked potentials. Evokedpotentials, such as, for example, SSEPs, are small bioelectric signalswith amplitudes as small as one microvolt or less.

Techniques have been developed to reduce random noise present inprocessed biosignals. Unfortunately, current techniques are notsufficient. Interference remaining in the processed signal when usingcurrent techniques can significantly distort the processed signal.Accordingly, there is a need for improved signal acquisition and/orprocessing systems and techniques capable of further reducing oreliminating interference in the processed signal.

SUMMARY

There is a significant need for improved intraoperativeelectrophysiological monitoring devices and methods that enable reliableacquisition and display of desired biological signals. There is a needfor medical devices capable of acquiring and displaying waveforms thataccurately and precisely match biological signals generated by apatient's body in response to stimuli. There is a need for signalprocessing devices and methods that eliminate or substantially eliminatethe presence of electrical interference, caused by electrical surgicaldevices, within processed signals. Embodiments provided herein mayaddress one or more of these needs.

Embodiments described herein generally relate to improved devices,components, systems, and methods for acquiring and isolating evokedpotential signals and/or other biosignals detected during surgery.Various embodiments relate to devices, systems, and methods forprocessing a recorded signal in such a manner that interference fromelectric surgical devices is reduced or eliminated while the targetbiosignal is maintained.

One aspect of the disclosure relates to methods for detecting changes innerve functioning within a subject. The methods can utilize any of thedevices, apparatuses and systems described herein. The methods caninclude receiving one or more biosignals, such as evoked potentials,from a patient, as an input at a biosignal detection device. The methodscan further include obtaining a processed signal having minimalelectronic interference or background noise contaminating the processedsignal, wherein such a processed signal is obtained by reducing,blocking, ignoring, or disregarding detected signals received when highfrequency electronic interference or background noise is present. Themethods can further include comparing at least two processed signalreceived at different time periods, and identifying a change in thebiosignals based upon the comparison of the at least two processedsignals. In some embodiments, the biosignals can be evoked potentialsfrom peripheral nerves. In some embodiments, the methods can furtherinclude detecting a nerve injury during a medical procedure or while asubject is not conscious, including, but not limited to a positioningeffect based on changes observed between the at least two processedsignals.

Another aspect of the disclosure is directed to a method performed by anamplifier system within a biosignal monitoring device. In variousembodiments, the method includes: receiving a threshold level input froma user via a user interface; receiving a first detected signal along afirst signal line, wherein the first detected signal comprises a targetbiosignal and high frequency noise; filtering the first detected signalto reduce the high frequency noise in the first detected signal;amplifying the first detected signal to increase a magnitude of thebiosignal; converting the first detected signal from analog to digitalfor data acquisition by a microprocessor; receiving a second detectedsignal along a second signal line, wherein the second detected signalcomprises the target biosignal and the high frequency noise; comparingthe second detected signal to the threshold level to determine whetherthe second detected signal or the threshold level is greater; and upondetecting that the second detected signal is greater than the thresholdlevel, performing one or more steps to suspend acquisition of the firstdetected signal.

In some embodiments, the one or more steps performed to suspendacquisition of distorted signals includes: suspending acquisition andstorage of digital data by a microprocessor, wherein the digital data isreceived from an analog to digital converter of the first signal line,and wherein the digital data is a digitized first detected signal.Additionally or alternatively, in some embodiments, the one or moresteps performed to suspend acquisition of distorted signals comprises:transmitting an interrupt signal along a control line to an amplifierwithin the first signal line, wherein the interrupt signal causes theamplifier to temporarily suspend operation. In some such embodiments,the amplifier suspends operation for approximately 5 to approximately 60seconds. In other embodiments, the amplifier suspends operations untilthe second detected signal is no longer detected to be greater than thethreshold level, or until a defined time thereafter. In otherembodiments, the amplifier suspends operation until transmission of theinterrupt signal ceases.

Another aspect of the disclosure is directed to a non-transitorycomputer readable medium, which stores instructions. In someembodiments, the instructions, when implemented, cause a processor toperform a method, such as, for example, an embodiment of the methoddescribed above.

A further aspect of the disclosure is directed to an automated devicefor isolating a target evoked potential or other biosignal from highfrequency noise present in a recorded signal. In some embodiments, thedevice includes a non-transitory computer readable medium, such as thecomputer readable medium described above or elsewhere in thisdisclosure. In some embodiments, the device further includes: aprocessor configured to execute instructions stored on thenon-transitory computer readable medium; a signal input configured tocouple to a recording electrode; and a data output configured to sendprocessed data to a user interface.

An additional aspect of the disclosure is directed to an amplifiersystem. In various embodiments, the amplifier system comprises a firstsignal pathway and a second signal pathway, each signal pathway havingan input for a detected signal, wherein the detected signal comprises atarget signal and high frequency interference. The first signal pathwayis configured to amplify the target signal. In various embodiments, thefirst signal pathway includes, at least: a low pass filter, anamplifier, an analog to digital converter, and a microprocessor. Invarious embodiments, the low pass filter output is electrically coupledto the amplifier, the amplifier output is electrically coupled to theanalog to digital converter (ADC), and the ADC output is electricallycoupled to the microprocessor. The second signal pathway is configuredto detect the high frequency interference. In various embodiments, thesecond signal pathway includes, at least: a band pass filter or highpass filter electrically coupled to a radiofrequency detector, acomparator, a digital to analog converter, and the microprocessor of thefirst signal pathway. The comparator of various embodiments isconfigured to compare signal sizes of a first signal entering from afirst leg and a second signal entering from a second leg, the first legof the comparator being electrically coupled to an output from theradiofrequency detector, and the second leg being electrically coupledvia the digital to analog converter to an output from themicroprocessor. In various embodiments, the microprocessor iselectrically coupled to an output from the comparator and is configuredto detect the presence of high frequency interference within thedetected signal when the first signal is greater than the second signal.

In some embodiments of the amplifier system, the second signal is athreshold signal set by a user interacting with the microprocessor via auser interface.

In some embodiments, the amplifier system is configured to temporarilysuspend signal amplification upon detection of high frequencyinterference. Additionally or alternatively, in some embodiments, theamplifier system is configured to temporarily suspend data acquisitionupon detection of high frequency interference. In some embodiments, theamplifier system additionally includes a control line electricallyconnecting the microprocessor to the amplifier of the first signalpathway, wherein the control line is configured to deliver an interruptsignal to the amplifier upon detection of high frequency interference.

In some embodiments, the amplifier system further includes one or morelow pass filters positioned between the comparator and themicroprocessor. In some embodiments, the band pass filter of the secondsignal pathway is formed of, or includes, one or more inductors,capacitors, or a combination thereof, configured to pass a frequencyband of interest while eliminating signals outside the frequency band ofinterest. In some such embodiments, the frequency band of interest is200 kHz to 6 MHz.

In some embodiments of the amplifier system, the radiofrequency detectoris formed of, or includes, an ultrafast diode, a capacitor connected toground, and a parallel shunt resistor connected to ground.

In some embodiments, the target signal is a biological signal. In atleast some such embodiments, the biological signal is an evokedpotential.

Yet another aspect of the disclosure is directed to a system forrecording a non-distorted evoked potential. In various embodiments, thesystem includes: a signal output operable to couple directly orindirectly to a stimulating electrode to deliver an electrical stimulusto a body; a signal input operable to couple directly or indirectly to arecording electrode to receive a detected signal, wherein the detectedsignal includes high frequency interference and an evoked potentialgenerated by the body's nervous system in response to the electricalstimulus; and a processing circuit coupled to the signal input. Invarious embodiments, the processing circuit includes: a microprocessorconfigured to process and analyze a recorded signal, and an amplifiersystem. The amplifier system includes: a first signal path configured toamplify the evoked potential, and a second signal path configured todetect the high frequency interference. In various embodiments, thefirst signal path and the second signal path are both connected to themicroprocessor, and the microprocessor is further configured to suspenddata acquisition from the first signal path and suspend amplificationwithin the amplifier of the first signal path upon detection of highfrequency interference within the detected signal.

In some embodiments of the system, the first signal path includes onlyor at least: a low pass filter, an amplifier, an analog to digitalconverter, and the microprocessor. In some embodiments, the secondsignal path includes a band pass filter, a radiofrequency detector, acomparator, one or more low pass filters, a digital to analog converter,and the microprocessor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a functional block diagram of one embodiment of a systemfor monitoring nerve function.

FIG. 2 depicts a block diagram of an amplifier system known in the priorart.

FIG. 3 depicts a block diagram of one embodiment of an amplifier systemconstructed in accordance with the principles of the present disclosure.

FIG. 4 depicts a block diagram of another embodiment of an amplifiersystem constructed in accordance with the principles of the presentdisclosure.

FIG. 5 depicts a circuit diagram of one embodiment of a radiofrequencydetector present within the amplifier system of FIG. 4.

FIG. 6 depicts a flow chart of one embodiment of a method performed inaccordance with the principles of the present disclosure.

FIG. 7 depicts a functional block diagram of one embodiment of acomputer system that may be used in association with, in connectionwith, and/or in place of certain embodiments of the systems andcomponents described herein.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form part of the present disclosure. Theembodiments described in the drawings and description are intended to beexemplary and not limiting. As used herein, the term “exemplary” means“serving as an example or illustration” and should not necessarily beconstrued as preferred or advantageous over other embodiments. Otherembodiments may be utilized and modifications may be made withoutdeparting from the spirit or the scope of the subject matter presentedherein. Aspects of the disclosure, as described and illustrated herein,can be arranged, combined, and designed in a variety of differentconfigurations, all of which are explicitly contemplated and form partof this disclosure.

Definitions

Unless otherwise defined, each technical or scientific term used hereinhas the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. In accordance with the claimsthat follow and the disclosure provided herein, the following terms aredefined with the following meanings, unless explicitly stated otherwise.

The term “about” or “approximately,” when used before a numericaldesignation or range (e.g., pressure or dimensions), indicatesapproximations which may vary by (+) or (−) 5%, 1% or 0.1%.

The term “substantially,” when used in the context of substantiallyeliminating electrical interference, shall mean eliminating at least80%, at least 90%, at least 95%, or at least 99% of the interferencepresent in a detected signal.

As used in the specification and claims, the singular form “a”, “an”,and “the” include both singular and plural references unless the contextclearly dictates otherwise. For example, the term “an evoked potential”may include, and is contemplated to include, a plurality of evokedpotentials. At times, the claims and disclosure may include terms suchas “a plurality,” “one or more,” or “at least one;” however, the absenceof such terms is not intended to mean, and should not be interpreted tomean, that a plurality is not conceived for a particular embodiment.

As used herein, the term “comprising” or “comprises” is intended to meanthat the devices, systems, and methods include the recited elements, andmay additionally include any other elements. “Consisting essentially of”shall mean that the devices, systems, and methods include the recitedelements and exclude other elements of essential significance to thecombination for the stated purpose. Thus, a device or method consistingessentially of the elements as defined herein would not exclude othermaterials or steps that do not materially affect the basic and novelcharacteristic(s) of the claimed invention. “Consisting of” shall meanthat the devices, systems, and methods include the recited elements andexclude anything more than a trivial or inconsequential element or step.Embodiments defined by each of these transitional terms are within thescope of this disclosure.

“Biosignal” or “biological signal” shall refer to any detectablewaveform generated from a living body, such as, for example, an evokedpotential, an EEG, EMG, or ECG.

“Evoked potential” shall mean any electrical potential recorded from thenervous system, which results from the application of a stimulus to aportion of the body. Evoked potentials include, for example,somatosensory evoked potentials (SSEPs), visual evoked potentials(VEPs), motor evoked potentials (MEPs), and brain stem auditory evokedpotentials (BAEPs).

“Somatosensory evoked potentials,” also known as “SSEPs” or “SEPs,” andreferred to herein as “SSEPs,” shall refer to electrical signalsgenerated by the nervous system in response to an electrical stimulationof a peripheral nerve.

One of ordinary skill in the art will appreciate that while manyembodiments disclosed herein are described in the context of detectionand isolation of SSEPs for the sake of simplicity of the description,various embodiments may also detect MEPs, VEPs, other evoked potentials,and/or other biosignals.

System Overview

Various embodiments provided herein are directed to improved systems,components, and methods for detecting and recording biosignals, such asevoked potentials, that are free of distortion from high frequencyinterference. FIG. 1 depicts a block diagram of a system 100 forautomatically detecting evoked potentials in accordance with oneembodiment of the present disclosure. As described in more detail below,the system 100 may include circuitry and/or other components thatsignificantly improve the system's ability to acquire clean evokedpotentials free of high frequency interference. In the depictedembodiment, the system 100, which may be coupled to a patient 101,includes, but is not limited to, one or more recording electrodes 112,one or more stimulating electrodes 122, an evoked potential detectiondevice (EPDD) 140, and a display unit 160. The stimulating and recordingelectrodes are each positioned over, near, in contact with, and/oraround a nervous system structure, such as the brain, the spinal cord,or a nerve. The electrodes may be needle electrodes, surface electrodes,cuff electrodes, or any other suitable electrode type.

In various embodiments, the EPDD 140 is electronically coupled to therecording electrodes 112 and stimulating electrodes 122 via a pluralityof cables 130. The EPDD 140 of various embodiments forms part of, iscoupled to, and/or includes a computer, such as, for example, thecomputer described in further detail with reference to FIG. 7. Asdescribed in the discussion of FIG. 7, the specialized computing deviceincludes a processor and memory and stores programmed instructions. Theinstructions, when executed by the processor, cause the device to: (1)deliver stimulations (in the form of electric current or voltage) to thestimulating electrodes, and (2) record detected signals picked up at therecording electrodes.

In various embodiments, the stimulating electrode 122 may beincorporated into the EPDD 140, coupled to the EPDD 140, or attachable,directly or indirectly to the EPDD 140. According to an exemplaryembodiment, the EPDD 140 sequentially stimulates one or more peripheralnerves via the stimulating electrode 122 while recording the SSEPs viathe recording electrode 112. According to an exemplary embodiment, theEPDD 140 includes an output operable to couple to the stimulatingelectrodes 122. The recording electrodes 112 of various embodiments maybe incorporated into the EPDD 140, coupled to the EPDD 140, orattachable, directly or indirectly to the EPDD 140. According to anexemplary embodiment, the EPDD 140 includes an input operable to couplethe EPDD 140 to the recording electrode 112.

The specialized computing device processes the recorded signal andtransmits data indicative of the processed signal to a display unit 160for display. Healthcare professionals may then monitor the display forchanges in the processed signal. In various embodiments, the EPDD 140 iselectrically, electronically, and/or mechanically coupled to the displayunit 160 via a link 150. In some embodiments, the link 150 is internalwiring or external cable. In some embodiments, the link 150 is awireless communication link. For example, in some embodiments, the EPDD140 is wirelessly coupled to the display unit 160 via Bluetooth® orother radiofrequency signal or via near field communications or acellular signal.

According to an exemplary embodiment, the system 100 is configured tomonitor SSEPs. In one such embodiment, the stimulating electrodes 122are configured for placement on the arms or legs of a patient 101 overperipheral nervous structures such as, for example, the ulnar nerves,median nerves, peroneal nerves, and/or posterior tibial nerves. In someembodiments, the stimulating electrodes 122 are intended for placementat the wrists and/or ankles of a patient so that the electrodes arelocated over, on, adjacent to, or near the ulnar nerves and/or posteriortibial nerves.

The recording electrodes 112 of some embodiments are configured forplacement at the trunk, spine, neck, and/or head. In some embodiments,the recording electrodes 112 are intended to be placed on, at, over, ornear one or more of the following locations: the scalp, cervicalvertebra, the forehead, the left and right Erb's points near theclavicle, and the left and right Popliteal Fossa just above the knee, orother points of nerve transmission that allow recording.

According to an exemplary embodiment, the EPDD 140 applies electricalstimulation to peripheral nerves of a patient by sending electricalpulses to the stimulating electrodes 122 located on some or all of apatient's limbs. Repeated stimulation elicits a response of thepatient's nervous system in the form of SSEPs, which travel up theperipheral nerves, through the dorsal column of the spinal cord, and tothe brain. With the right equipment, SSEPs can be detected and changesin the evoked potential can be monitored to assess changes in nervefunction. In an exemplary embodiment, the EPDD 140 uses the recordingelectrodes 112 to detect signals generated from the patient, includingSSEPs. The EPDD 140 of some embodiments includes hardware, software, ora combination thereof to selectively record and process the detectedsignal to generate a meaningful signal for display. In order to produceand display meaningful data, the recorded signal should be free orsubstantially free of interference, for example, interference caused byelectric surgical devices.

Introduction

Conventionally, the recorded signal of prior art evoked potentialmonitoring systems includes a target signal (e.g., an evoked potential)and random background noise, including EEG signals. At various timesduring surgery, the recorded signal may also include non-random highfrequency electrical interference caused by electric tools or otherdevices used during surgery. The interference within the recorded signalcan greatly distort the signal such that, even with processing, it isnot an accurate representation of the target evoked potential.

Accordingly, in order for the processed signal to be most meaningful andthe monitoring to be most effective, it would be beneficial if therecorded and/or processed signal was free or substantially free ofsignificant noise and interference. This is a particular concern forevoked potentials, because even the presence of a little noise candramatically reduce the signal-to-noise ratio due to the small size ofevoked potentials. Evoked potentials, such as, for example, SSEPs, aresmall bioelectric signals with amplitudes as small as one microvolt orless. In comparison, the amplitude of many other recorded biologicalsignals, such as EEG, EMG, and ECG, tend to be much larger. A typicalEEG is usually 10 or more microvolts, EMG is one or more millivolts andan ECG signal can be hundreds of millivolts. The relative size of theseother biological signals has meant that acquiring and monitoring suchsignals has been much easier to incorporate into standard surgicalpractice. In contrast, despite the clinical utility of evokedpotentials, their small size has limited their use to specializedsurgeries that justify having a technologist and/or neurologist present.

Due to their small size, recording evoked potentials reliably withexisting prior art technology is difficult and requires a person withexpertise in the practice to ensure that electrical interference isminimized. The smaller the biological signal, the more important it isto limit the noise contamination of the recording. Noise is producedwhen other electrical signals are picked up by, and coupled into, therecording circuits of the monitoring system. This contaminating noisecan occur at any point along the acquisition circuit, including withinthe patient, at the site of the electrodes, within the cables carryingthe unamplified signals, and at the location of signal amplifiers.

To record evoked potentials in an electrically noisy environment such asthe operating room, surgical technologists currently employ a myriad oftechniques to increase the signal-to-noise ratio of the evokedpotential.

For example, many employ a signal averaging technique developed byDawson in 1954. The signal averaging technique increases the signal tonoise ratio by averaging time-locked stimulus-triggered sweeps. Dawson'ssignal averaging technique relies on the fact that evoked potentialwaveforms occur with a constant latency following each stimulus (barringchanges in nervous system health or functionality), whereas most noiseis random and will eventually average to near zero levels aftersuccessive stimuli. The signal averaging technique is helpful, forexample, in reducing the effect of electroencephalogram (EEG) noise inthe processed signal. The EEG is a relatively random signal arising fromactivity in the outer layers of the cortex. Accordingly, to extractevoked potential waveforms from the background noise, the surgicaltechnologist generally uses an IONM system that applies successivetime-locked stimuli. Multiple stimulus time locked recording epochs areaveraged together. For example, IONM systems may stimulate peripheralnerves at a frequency of 2 to 5 Hz, and waveforms are acquired andaveraged for analysis when 100 to 500 stimuli have been delivered.

Unfortunately, in a surgical setting, not all electrical interference israndom, and some interference is so large that it cannot be removed viasignal averaging or other currently available filtering techniques. Inparticular, a substantial amount of interference may be generated byelectric surgical tools. The most common interference comes from theElectrosurgical Unit (ESU), also known as an RF knife or Bovie, used tocut and cauterize tissue in the operating room. When an ESU is enabled,typically there is a large amount of very high frequency contentinterference mixed with the biosignals of interest. This interference isoften non-random and so large that the system is unable to remove thisinterference using the normal means of averaging the most recent sweepwith other time locked sweeps.

In order for intraoperative neurophysiologic monitoring or otherelectrophysiological monitoring to be effective, it is desirable to keepthe ESU-generated interference out of the signal of interest. Currentmeans of ignoring ESU-generated interference have significantshortcomings. For example, currently, the most common method of keepingthe ESU-generated interference out of the signal of interest is a mentalprocess, performed by a neuro-monitoring specialist, which compares thedisplayed signal to a maximum positive or negative value of ananalog-to-digital converter (ADC) in the system. In particular, manyspecialists in the field will simply assume a signal is contaminatedwith noise from the ESU and reject or disregard the signal if it getswithin a particular threshold value, for example, 95%, of the maximumpositive or negative value of the system's ADC.

Such an approach is lacking in sensitivity and specificity. Low levelsof ESU interference may avoid rejection and still be present in thesignal, and lowering the filter level to capture these low levels of ESUinterference may cause rejection of normal evoked potential signals tooand increase the time required to obtain a good SSEP waveform. Otherspecialists mentally disregard changes to waveforms that are observedwithin a time frame following the use of an ESU. Still othertechnologists turn off signal acquisition manually when an ESU is inuse. This can be a tedious process since ESUs are used frequently duringsurgery to cut and cauterize tissue, and this process can result inmissed changes in nervous system functioning, if signal acquisitionremains off for too long and the changes occur during the time that thesignal acquisition is in the off mode.

An alternate method to remove the ESU interference from a signal is tolook at the frequency content of the signal coming from the patient. TheESU interference has an output frequency of between 200 kHz and 6 MHz.This is dramatically different from the biosignal of interest which hasa frequency of less than 10 kHz. However, in typical evoked potentialmonitors, there is no ability to separately detect signals havingfrequencies as high as ESU-generated interference, because there arelow-pass hardware filters in the signal path. These systems are notintended to view such high frequency content. Given the typical signalsof interest, the systems are generally constructed such that there is nomeans for looking at signals with frequency content substantially higherthan 10 kHz.

The above-described human judgment-based approaches to ESU interference“filtering” are error-prone and lacking in precision and accuracy.Additionally, as IONM devices become used in more surgeries, there willnot be enough neuro-monitoring specialists to attend to each surgery.For this and other reasons, more automated IONM devices, if effective,could be desirable. The development of automated IONM devices is limitedthough, in part, by the need for improved interference rejectionmethods. There is a need for signal filtering methods that are not basedon human judgment. Accordingly, in order to facilitate automation ofIONM devices and improve the accuracy and precision of displayed evokedpotential waveforms, improved biosignal-isolating techniques are needed.

Accordingly, the EPDD 140 of various embodiments provided herein,includes circuitry, a processor, and memory with instructions storedtherein, which together function to prevent acquisition of random noiseand non-random electrical interference, including ESU-causedinterference, and produce a processed waveform representative of apatient's evoked potentials. The system 100 of various embodiments mayinclude one or more features intended to improve the sensitivity andspecificity of signal filtering. Various exemplary features aredescribed below.

Methods and Components for Minimizing Noise in a Recorded Signal

In various embodiments, the specialized system 100 can be programmed toperform the well-known signal averaging techniques developed by Dawsonto reduce the presence of random noise within the processed signal.

Additionally or alternatively, various embodiments of the systemdisclosed herein (such as, for example, the depicted system 100) includeone or more methods or means of automatically managing and minimizingnoise contamination within the recorded signal in order to automaticallygenerate reliable data. Specifically, in various embodiments, the system(such as system 100) is configured to automatically detect when ahigh-noise generating device, such as an ESU, is in operation. In someembodiments, the system temporarily suspends data acquisition and/orgrounds all received signals during the operation of an ESU. ESUs cutand cauterize tissue by applying electrical energy from aradio-frequency (RF) generator to the tip of the ESU. Thus, in anexemplary embodiment of the system 100, the EPDD 140 includes an RFreceiver configured to receive radio frequencies emitted from nearbyelectric surgical devices, such as an ESU. In some embodiments, the RFreceiver is included within an amplifier system in the EPDD 140. In someembodiments, when a threshold level of high frequency RF signals aredetected by the RF receiver of the EPDD 140, the system suspends signalacquisition or signal processing.

In order to detect when a high frequency noise generating device, suchas an ESU or other electric surgical tool, is in operation andtemporarily suspend data acquisition, various embodiments providedherein include the addition of an alternative signal path to a typicalevoked potential amplifier system.

A conventional evoked potential amplifier system is provided in FIG. 2for reference. Such an amplifier system is provided in at least someexisting IONM systems. In the amplifier system, a detected signal, whichincludes a target signal and high frequency interference, enters a lowpass filter. Only signal frequencies below a given threshold, such as,for example, 10 kHz, are allowed to pass. The portion of the signal thatpasses through continues on to an amplifier where the signal isamplified in magnitude, for example, by 100×, 1000×, or 10000×. Thisamplified signal is converted into a digital signal and passed to amicroprocessor for further signal processing and/or analysis.Problematically, noise fluctuates in frequency, even from typicallyhigh-frequency devices such as ESUs. Accordingly, the low pass filter isinsufficient to remove all noise from the detected signal, resulting innoise entering the amplifier. While evoked potentials have amplitudes assmall as 1 millivolt, the noise from electric surgical tools tends tohave much greater amplitudes. As a result, noise entering the amplifiercan quickly saturate the amplifier and distort the signal passed throughto the microprocessor.

One embodiment of a modified evoked potential amplifier system,constructed in accordance with the principles of the present disclosure,is shown in FIG. 3. The block diagram of FIG. 3 depicts variousfunctional or structural components present within an evoked potentialamplifier system. The depicted amplifier system may be included, forexample, within or coupled to the evoked potential detection device(EPDD) 140 of FIG. 1 for the purposes of filtering and amplifying thedetected signal. While the depicted embodiment and other embodimentsdescribed herein are often referred to as improved “evoked potentialamplifier systems,” it will be appreciated by those skilled in the artthat the improved amplifier systems described herein may be used tofilter and amplify any desired biosignal.

In the amplifier system of FIG. 3, a power splitter (not shown) and analternate signal path are provided to separate the signal of interestfrom high frequency interference. The power splitter of at least someembodiments directs low power signals, such as those in the 0.1-100millivolt range, to a primary path (shown in FIG. 3 as the upper path).Such signals are primarily composed of the target signals (e.g., evokedpotentials). Higher power signals (i.e., signals having a largeramplitude) are directed to an alternative path (shown in FIG. 3 as thelower path). The lower path is configured to enable detection of highfrequency noise. For example, the lower path includes a comparatorelectrically coupled to a microprocessor. The comparator compares thelevel of high frequency contamination in the lower path signal with athreshold level set by a user via the microprocessor. When the lowerpath signal is larger than the threshold level, the comparator outputs asignal to the coupled microprocessor. Said signal acts as an alert,alerting the microprocessor that high frequency interference is present.When high frequency noise is detected, the microprocessor delivers aninterrupt signal via a Control line to the amplifier of the primarypath. The interrupt signal causes the amplifier to temporarily suspendoperations. Such a system prevents the amplifier of the primary pathfrom getting saturated each time an electric surgical tool is usedduring surgery.

While the circuit of FIG. 3 is an improvement over the evoked potentialamplifier systems present within conventional IONM systems, it may notbe desirable in all settings. Since the evoked potential signals arevery small, any additional circuitry, such as a power splitter to splitthe recorded signal, on the signal line going to the first amplifierstage may decrease the quality of the amplified signal. Instead, analternate signal line to the patient (as shown and described withrespect to FIG. 4) may be preferred.

FIG. 4 provides a block diagram of the various functional and/orstructural components of one embodiment of a preferred evoked potentialamplifier system. As with FIG. 3 above, the amplifier system describedherein may be used to amplify any desired biosignal. The depictedcomponents may be included, for example, within the circuitry of theevoked potential detection device (EPDD) 140 of FIG. 1 in order tofilter and amplify the detected signal.

In the depicted embodiment, there are two possible paths of travel forinterference from electric surgical tools to enter the amplifier system:(1) through the air as a radio frequency electro-magnetic wave, or (2)as a conducted signal. In some embodiments, the preferred path is alongan unshielded wire that is capacitive coupled to the patient. Theunshielded wire may pick up electro-magnetic waves through the air andthe capacitive coupled line may pick up the conducted signal.

As shown, the alternative (e.g., lower) path depicted in FIG. 4 includesa band pass filter or high pass filter, an RF detector, a comparator,one or more low pass filters, a microprocessor, and a digital to analogconverter.

In the depicted embodiment, the band pass filter may be configured toallow signals to pass through only when they are within the typicalrange of signals generated by electric surgical tools. The band passfilter on the alternative signal line may be formed of, or include, oneor more inductors, capacitors, or a combination thereof, configured topass the frequency band of interest while eliminating signals outsidethe frequency band of interest. In some embodiments, the band passfilter may be a Butterworth filter, a Chebyshev filter, a Bessel filter,or any other type of filter known to a skilled person. In someembodiments, the band pass filter may be an active filter. In at leastsome embodiments, the frequency band of interest is, for example, 200kHz to 6 MHz. In an alternative embodiment, a high pass filter isprovided, which allows passage of signals above a given frequency, suchas, for example, above 200 kHz.

In various embodiments, signals passing through the first filter of thealternative pathway enter a radiofrequency (RF) detector. In somenon-limiting embodiments, the RF detector is formed of an ultrafastdiode (such as, for example, the Vishay ES07D-GS08), a capacitorconnected to ground, and a parallel shunt resistor connected to ground,as depicted in FIG. 5. In some embodiments, when a threshold level of RFsignals are detected, the signal in the alternative path enters acomparator.

The comparator may be a linear device such as, for example, the TexasInstruments differential comparator LM393. The comparator has two “legs”or signal sources, and the comparator is configured to compare signalsfrom the two legs to identify which signal is larger (e.g., which signalhas a greater amplitude). In some embodiments, one leg of the comparatoris connected to the output from the RF detector. In some embodiments,the other leg is electrically connected to the output from a Digital toAnalog Converter, which, in turn, is connected to the output from themicroprocessor. In such embodiments, the second leg is adjustable, forexample, adjustable in software. The comparator compares the level(e.g., the power level) of high frequency contamination in the recordedsignal with a threshold level (e.g., a threshold power level) set by auser via the microprocessor. The user may adjust the threshold levelusing the microprocessor. When the recorded signal in the alternativepath is larger than the threshold level set by the user, the signaloutput of the comparator (which may be filtered by a low pass filter)acts as an alert to the microprocessor, alerting the microprocessor thathigh frequency interference is present.

Upon receiving a signal alerting the microprocessor of high frequencyinterference, the microprocessor may reject the data received from theanalog to digital converter on the primary path. The microprocessor mayalso send an interrupt signal along a control line to the amplifier ofthe primary path, said interrupt signal causing the amplifier totemporarily suspend operation. Such steps may protect the hardware fromdamage and avoid data acquisition of distorted signals. In someembodiments, the amplifier may suspend operations for 10 seconds. Inother embodiments, the amplifier may suspend operations for 5 seconds,60 seconds, or any value therebetween. In various embodiments, theamplifier may suspend operations until the comparator no longer detectsthat the signal from the RF detector is greater than the threshold levelset by the user or until any defined time after that occurs. In someembodiments, when an electric surgical tool is no longer in use (i.e.,when the signal from the RF detector is no longer greater than thethreshold level set by the user), the microprocessor will no longer sendan interrupt signal to the amplifier of the primary path and theamplifier will automatically resume functioning. This control acts as,or similar to, a reverse squelch, only allowing a signal through theprimary path if the high frequency content is determined via thealternative path to be sufficiently low. A squelch normally only allowsa signal through that is sufficiently large.

In an alternate design, the output of the comparator can go directly tothe control line using logic circuitry instead of a software-mediatedmicroprocessor. This may reduce the latency by a few microseconds andbetter protect the system from interference.

In various embodiments, if the comparator senses high frequency contentthat is too high, the microprocessor may reject that data and protectthe amplifiers from any ill effects that could be caused by highfrequency signals. The microprocessor may adjust the level of highfrequency interference allowed into the signal so that the system canstill be used even if there is always noise in the environment. Thesystem can be adjusted to quiet operating rooms and get very cleansignals quickly and still operate in noisy environments where the numberof averages may be higher. In various embodiments, the microprocessorrejects any averages that are in the process of being acquired upondetection of high frequency noise (e.g., noise with a frequency above200 kHz). Since it is possible that there may be other types ofinterference in addition to interference from electric surgical tools,the established level detection methods may be operated in parallel withthe frequency specific system and method described herein.

One method performed by an amplifier system, such as the amplifiersystem of FIG. 4, is provided in FIG. 6. As shown, at block 602, in someembodiments, the amplifier system receives a threshold level input froma user via a user interface. The user interface may form part of, or beconnected to, a microprocessor. The threshold level may be set, forexample, to match a known power level of an ESU or other electricalequipment present in an operating MOM.

At block 604, the amplifier system receives a first detected signalalong a first signal line. The first detected signal includes a targetbiosignal and high frequency noise. At block 606, the amplifier systemfilters the first detected signal to reduce the high frequency noise inthe first detected signal. Such filtering may be performed, for example,by a low pass filter. At block 608, the amplifier system amplifies thefirst detected signal to increase a magnitude of the target biosignal.Such amplification may be performed by an amplifier. At block 610, theamplifier system converts the first detected signal from analog todigital for data acquisition by the microprocessor.

At block 612, the amplification system receives a second detected signalalong a second signal line, such as, for example, an unshielded wirecapacitively coupled to a patient. Like the first detected signal, thesecond detected signal also includes the target biosignal and the highfrequency noise. At block 614, the amplification system compares thesecond detected signal to the threshold level to determine whether thesecond detected signal or the threshold level is greater. For example,the amplitude or power level of the second detected signal may becompared to the threshold level. In some embodiments, the seconddetected signal is filtered via a band pass filter or high pass filterand accumulated and/or averaged by an RF detector before being comparedto the threshold level.

As shown at block 616, upon detecting that the second detected signal isgreater than the threshold level, the amplifier system may perform oneor more steps to suspend acquisition of the first detected signal. Forexample, the amplifier system may: suspend acquisition and storage ofdigital data at the microprocessor, and/or deliver an interrupt signalalong a Control line to an amplifier within the first signal line,wherein the interrupt signal causes the amplifier to temporarily suspendoperation. In some such embodiments, the amplifier suspends operationfor approximately 5 to approximately 60 seconds. In other embodiments,the amplifier suspends operations until the second detected signal is nolonger detected to be greater than the threshold level, or until adefined time thereafter. In other embodiments, the amplifier suspendsoperation until transmission of the interrupt signal ceases.

The components and methods described above can be included in, andperformed by, any biosignal monitoring apparatus, such as, for example,the evoked potential detection device (EPDD) 140 of FIG. 1. In variousembodiments, the components and methods described above result in thegeneration of clean processed signals that are free or substantiallyfree of high frequency interference. As described above, in variousembodiments, the components and methods of the present technology causea biosignal monitoring device to automatically suspend data acquisitionand amplifier operations when high frequency signals are detected. Thus,in various embodiments, the components and methods of the presenttechnology cause a biosignal monitoring device to automatically suspenddata acquisition and amplifier operations any time an ESU or otherelectric surgical tool is in use. The components and methods may alsocause the biosignal monitoring device to automatically resume dataacquisition and amplifier operations when the electric surgical tool isno longer in use. In such a manner, the components and methods are ableto keep high frequency interference out of the processed signal.Accordingly, the processed signal that is generated in variousembodiments is an accurate and precise representation of a patient'sbiosignals. By generating clean processed signals, biosignal monitoringapparatuses of the present technology are able to monitor a patient'sbiosignals for changes. The biosignals may be monitored by a healthcareprofessional viewing a display screen that displays the processedbiosignals, and/or the biosignal monitoring device may automaticallymonitor the biosignals for changes. In some embodiments, changes inlatency, amplitude, and/or morphology may be indicative of an injury tothe central or peripheral nervous system. As described, for example, inU.S. Pat. No. 8,731,654 to Johnson et al., the disclosure of which isherein incorporated by reference in its entirety, the monitoring devicesof some embodiments are configured to automatically identify positioningeffect in a patient based on changes in the patient's evoked potentials.Such embodiments are possible when the processed signal is an accurateand precise representation of the patient's biosignals.

The Microprocessor

In preferred embodiments, the EPDD 140 of FIG. 1 includes a processor,connected circuitry, and memory storing instructions, which togetheroperate to amplify and filter the detected signal as described above. Invarious embodiments, the memory, processor, and circuitry are componentsof a specialized computer, and in at least some such embodiments, theEPDD 140 forms part of, is coupled via a wired or wireless connectionto, and/or includes said computer. Additionally, in some embodiments,the system 100 includes one or more user interfaces to receive inputsfrom a user and provide outputs to the user. Such user interfaces mayform part of the computer or may be in electrical or wirelesscommunication with the computer. A discussion of the components of anexample computer are provided below. The discussion is intended to benon-limiting as one skilled in the art will appreciate that any numberof computer architectures may be suitable for use in, with, or as theevoked potential detection device. In some embodiments, the describedcomputer forms the microprocessor shown in FIG. 3 and/or FIG. 4.

FIG. 7 depicts a block diagram of one example embodiment of a computersystem that may form part of any of the systems described herein.Specifically, FIG. 7 illustrates an example computer 200, which may runan operating system such as, for example, MICROSOFT® WINDOWS®NT/98/2000/XP/CE/7/VISTA/RT/8, etc. available from MICROSOFT®Corporation of Redmond, Wash., U.S.A., SOLARIS® from SUN® Microsystemsof Santa Clara, Calif., U.S.A., OS/2 from IBM® Corporation of Armonk,N.Y., U.S.A., iOS or Mac/OS from APPLE® Corporation of Cupertino,Calif., U.S.A., or any of various versions of UNIX® (a trademark of theOpen Group of San Francisco, Calif., USA) including, e.g., LINUX®,HPUX®, IBM AIX®, and SCO/UNIX®, or Android® from Google®, Inc. ofMountain View, Calif., U.S.A., etc. Such operating systems are providedfor example only; the system embodiments described herein may beimplemented on any appropriate computer system running any appropriateoperating system.

The computer system 200 may include one or more processors, such asprocessor(s) 204. The processor(s) 204 may be connected to acommunication infrastructure 206 (for example, a communications bus,cross-over bar, or network, etc.). Various software embodiments may bedescribed in terms of this example computer system. After reading thisdescription, it will become apparent to a person skilled in the relevantart how to implement the described methods using other computer systemsand/or architectures.

Computer system 200 may include a display interface 202 to forwardgraphics, text, and other data, etc., from the communicationinfrastructure 206 for display on the display unit 230.

The computer system 200 may also include, e.g., but may not be limitedto, a main memory 208, random access memory (RAM), and a secondarymemory 210, etc. The secondary memory 210 may include, for example, (butmay not be limited to) a hard disk drive 212 and/or a removable storagedrive 214, representing a floppy diskette drive, a magnetic tape drive,an optical disk drive, a magneto-optical disk drive, a compact diskdrive CD-ROM, a digital versatile disk (DVD), a write once read many(WORM) device, a flash memory device, etc. The removable storage drive214 may read from and/or write to a removable storage unit 218 in awell-known manner. Removable storage unit 218 may represent, forexample, a floppy disk, a magnetic tape, an optical disk, amagneto-optical disk, a compact disk, a flash memory device, etc. whichmay be read from and written to by removable storage drive 214. As willbe appreciated, the removable storage unit 218 may include a computerusable storage medium having stored therein computer software and/ordata.

In alternative exemplary embodiments, secondary memory 210 may includeother similar devices for allowing computer programs or otherinstructions to be loaded into computer system 200. Such devices mayinclude, for example, a removable storage unit 222 and an interface 220.Examples of such may include a program cartridge and cartridge interface(such as, e.g., but not limited to, those found in some video gamedevices), a removable memory chip (such as, e.g., but not limited to, anerasable programmable read only memory (EPROM)), or programmable readonly memory (PROM) and associated socket, and other removable storageunits 222 and interfaces 220, which may allow software and data to betransferred from the removable storage unit 222 to the computer system200.

The computer 200 may also include an input device 216 such as, forexample, a mouse or other pointing device such as a digitizer, atouchscreen, a microphone, a keyboard, and/or other data entry device.The computer 200 may also include output devices 240, such as, forexample, a display 230 and/or display interface 202. The computer 200may include input/output (I/O) devices such as a communicationsinterface 224, a cable 228, and/or a communications path 226, etc. Thesedevices may include but are not limited to a network interface card andmodems. The communications interface 224 may allow software and data tobe transferred between the computer system 200 and external devices.Examples of a communications interface 224 include, for example, amodem, a network interface (such as, e.g., an Ethernet card), acommunications port, a Personal Computer Memory Card InternationalAssociation (PCMCIA) slot and card, etc. Software and data transferredvia the communications interface 224 may be in the form of signals 228which may be electronic, electromagnetic, optical, or other signalscapable of being received by the communications interface 224. Thesesignals 228 may be provided to the communications interface 224 via, forexample, a communications path 226 such as a channel. This channel 226may carry signals 228, for example propagated signals, and may beimplemented using, for example, wire or cable, fiber optics, a telephoneline, a cellular link, a radio frequency (RF) link and othercommunications channels, etc.

In various embodiments described herein, wired networks may include anyof a wide variety of well-known means for coupling voice and datacommunications devices together. In various embodiments describedherein, wireless network types may include, but are not limited to, forexample, code division multiple access (CDMA), spread spectrum wireless,orthogonal frequency division multiplexing (OFDM), 1G, 2G, 3G, or 4Gwireless, Bluetooth, Infrared Data Association (IrDA), shared wirelessaccess protocol (SWAP), “wireless fidelity” (Wi-Fi), WIMAX, and otherIEEE standard 802.11-compliant wireless local area network (LAN),802.16-compliant wide area network (WAN), and ultra-wideband (UWB)networks, etc.

Some embodiments may include or otherwise make reference to WLANs.Examples of a WLAN may include a shared wireless access protocol (SWAP)developed by Home radio frequency (HomeRF), and wireless fidelity(Wi-Fi), a derivative of IEEE 802.11, advocated by the wireless Ethernetcompatibility alliance (WECA). The IEEE 802.11 wireless LAN standardrefers to various technologies that adhere to one or more of variouswireless LAN standards. An IEEE 802.11 compliant wireless LAN may complywith any of one or more of the various IEEE 802.11 wireless LANstandards including, for example, wireless LANs compliant with IEEE std.802.11a, b, d, g, or n, such as, e.g., but not limited to, IEEE std.802.11 a, b, d, g, and n (including, e.g., but not limited to IEEE802.11g-2003, etc.), etc.

Some embodiments described herein are directed to the apparatuses and/ordevices for performing the operations described herein. Such anapparatus may be specially constructed for the desired purposes, or itmay comprise a general purpose device selectively activated orreconfigured by a program stored in the device to perform thespecialized purpose.

In one example embodiment, the EPDD 140 sends data to an external userinterface, such as a monitor, smartphone, or tablet, for display to theuser. The communications interface 224 allows data to be transferredbetween the computer system 200 and the external user interface. In someembodiments, the communications interface 224 is a USB port or otherport configured to receive a cable connected to the external userinterface. In other embodiments, the communications interface 224 is acellular, Wi-Fi, or RF antenna or other interface for wirelesscommunications. The antenna of various embodiments acts both atransmitter and receiver.

Other embodiments described herein are directed to instructions storedon a machine-readable medium, which may be read and executed by acomputing platform to perform operations described herein. Amachine-readable medium may include any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, an exemplary machine-readable storage medium mayinclude: read only memory (ROM); random access memory (RAM); magneticdisk storage media; optical storage media; magneto-optical storagemedia; flash memory devices; other exemplary storage devices capable ofstoring electrical, optical, acoustical, or other form of propagatedsignals (e.g., carrier waves, infrared signals, digital signals, etc.)thereon, and others. Computer programs (also called computer controllogic), may include object oriented computer programs, and may be storedin main memory 208 and/or the secondary memory 210 and/or removablestorage units 214, also called computer program products. Such computerprograms, when executed, may enable the computer system 200 to performthe features of the present technology. In particular, the computerprograms, when executed, may enable the processor or processors 204 toprovide a method for filtering and processing an evoked potential signalaccording to an exemplary embodiment.

Another exemplary embodiment is directed to a computer program productcomprising a computer readable medium having control logic (computersoftware) stored therein. The control logic, when executed by theprocessor 204, may cause the processor 204 to perform functionsdescribed herein. In other embodiments, various functions describedherein may be implemented primarily in hardware using, for example, butnot limited to, hardware components such as application specificintegrated circuits (ASICs), an integrated circuit board with variouscircuit components, or one or more state machines, etc. Implementationof the hardware state machine so as to perform the functions describedherein will be apparent to persons skilled in the relevant art. In someembodiments, signal filtering, processing, and other described functionsmay be implemented using one or a combination of any of hardware,firmware, software, etc.

The computer program mediums and computer readable mediums describedherein may provide software to computer system 200. The softwareincludes a self-consistent sequence of acts or operations leading to adesired result. These include physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers or the like. It should be understood, however, that allof these and similar terms are to be associated with the appropriatephysical quantities and are merely convenient labels applied to thesequantities.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it may be appreciated that throughout the specificationdiscussions utilizing terms such as “processing,” “computing,”“calculating,” “determining,” or the like, refer to the action and/orprocesses of a computer or computing system, or similar electroniccomputing device, that manipulate and/or transform data represented asphysical, such as electronic, quantities within the computing system'sregisters and/or memories into other data similarly represented asphysical quantities within the computing system's memories, registers orother such information storage, transmission or display devices.

In a similar manner, the term “processor” may refer to any device orportion of a device that processes electronic data from registers and/ormemory to transform that electronic data into other electronic data thatmay be stored in registers and/or memory. A “computing platform” maycomprise one or more processors.

According to an exemplary embodiment, exemplary methods set forth hereinmay be performed by an exemplary one or more computer processor(s)adapted to process program logic, which may be embodied on an exemplarycomputer accessible storage medium, which when such program logic isexecuted on the exemplary one or more processor(s), may perform suchexemplary steps as set forth in the exemplary methods.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

Those of skill in the art will appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans may implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present disclosure.

Although the foregoing has included detailed descriptions of someembodiments by way of illustration and example, it will be readilyapparent to those of ordinary skill in the art in light of the teachingsof these embodiments that numerous changes and modifications may be madewithout departing from the spirit or scope of the appended claims.

What is claimed is:
 1. An amplifier system, comprising: an evokedpotential detection device including at least one data processor and atleast one memory storing instructions for stimulating a peripheral nerveand recording one or more detected signals, the evoked potentialdetection device further comprising: a first signal pathway and a secondsignal pathway coupled with the evoked potential detection device, eachsignal pathway having an input for the detected signal, wherein thedetected signal comprises a target signal and high frequencyinterference, wherein the first signal pathway is configured to amplifythe target signal and comprises, in order: a low pass filter, anamplifier, an analog to digital converter, and a microprocessor; whereinthe second signal pathway is configured to detect the high frequencyinterference and comprises: a band pass filter or high pass filterelectrically coupled to a radiofrequency detector, a comparator, adigital to analog converter, and the microprocessor of the first signalpathway; wherein the comparator is configured to compare a firstamplitude of a first signal entering from a first leg and a secondamplitude of a second signal entering from a second leg, the first legof the comparator being electrically coupled to an output from theradiofrequency detector, and the second leg being electrically coupledvia the digital to analog converter to an output from themicroprocessor; wherein the microprocessor is electrically coupled to anoutput from the comparator and is configured to detect the presence ofhigh frequency interference within the detected signal when the firstamplitude is greater than the second amplitude; and wherein the evokedpotential detection device is configured to temporarily suspend dataacquisition upon detection of the high frequency interference.
 2. Theamplifier system of claim 1, wherein the second signal is a thresholdsignal set by a user interacting with the microprocessor via a userinterface.
 3. The amplifier system of claim 1, wherein the system isconfigured to temporarily suspend signal amplification upon detection ofhigh frequency interference.
 4. The amplifier system of claim 1, furthercomprising a control line electrically connecting the microprocessor tothe amplifier, wherein the control line is configured to deliver aninterrupt signal to the amplifier upon detection of high frequencyinterference.
 5. The amplifier system of claim 1, further comprising oneor more low pass filters positioned between the comparator and themicroprocessor.
 6. The amplifier system of claim 1, wherein the bandpass filter of the second signal pathway comprises one or moreinductors, capacitors, or a combination thereof, configured to pass afrequency band of interest while eliminating signals outside thefrequency band of interest.
 7. The amplifier system of claim 6, whereinthe frequency band of interest is 200 kHz to 6 MHz.
 8. The amplifiersystem of claim 1, wherein the radiofrequency detector comprises anultrafast diode, a capacitor connected to ground, and a parallel shuntresistor connected to ground.
 9. The amplifier system of claim 1,wherein the target signal is a biological signal.
 10. The amplifiersystem of claim 9, wherein the biological signal is an evoked potential.